Income Taxes - Additional Information (Detail) - USD ($)
 12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Income Tax Contingency [Line Items]      
Income tax benefit $ 0 $ 0 $ 0
Net operating loss for federal and state income tax 22,554,000 15,243,000  
Research and development tax credit carryforwards for federal and state income tax $ 4,052,000 $ 2,582,000  
Increased ownership percentage 50.00%    
Unrealized net operating loss carryforwards $ 1,876,000    
Federal [Member]      
Income Tax Contingency [Line Items]      
Net operating loss for federal and state income tax $ 60,831,000    
Operating loss carryforwards,expiration period 2026    
Research and development tax credit carryforwards for federal and state income tax $ 2,976,000    
Research and development tax credit carryforwards,expiration period 2026    
State [Member]      
Income Tax Contingency [Line Items]      
Net operating loss for federal and state income tax $ 50,492,000    
Operating loss carryforwards,expiration period 2029    
Research and development tax credit carryforwards for federal and state income tax $ 1,632,000    
Research and development tax credit carryforwards,expiration period 2025